Telephone system



9, 1932- R.-F. STEHLIK 1,870,471

TELEPHONE SYSTEM Filed NOV. 1, 1930 RUDOLPH FRANK STEHLIK, %M C2m4 Att Patented Aug. 9, 1932 UNETED STATES PATENT OFFECEL RUDOLPH FRANK STEHLIK, OF CHICAGO, ILLINOIS, ASSIGNOB TO ASSOCIATED TELE- PHONE & TELEGRAPH COMPANY, OF CHICAGO, ILLINOIS TELEPHONE SYSTEM Application filed November 1, 1930, Serial No.

The present invention relates to telephone systems and is more particularly concerned with systems in which local or internal service is obtained automatically and facilities are provided for obtaining connection to a public main exchange from the same instrument. It has already been suggested to provide an instrument for use in a system in which both local and outside connections are obtained by dialling or the former by dialling and the latter with the help of an operator. The present invention is concerned with the case in which the local system is of the socalled intercommunication type, that is to say the wanted party is selected by pressing a. particular button or equivalent operation rather than by dialling.

According to the invention the set is provided with the usual intercommunication push-button mechanism and also with a trunk key corresponding to each trunk line provided for out-service. Preferably also there is associated with each trunk line a visual indicator, for instance of the electromagnetic type, for indicating to all the stations when the trunk line is in use. The push button mechanism will preferably be arranged in known manner so that full depression of the button effects the signalling of the wanted station and that the button when released re mains in a partially depressed position to complete the talking circuit, being fully restored only when the switch hook is operated on replacement of the receiver. Preferably I also the trunk keys are interlocked with the push buttons in such manner that the operation of one key or button will release another previously depressed. In the case of the trunk keys, however, if a local push button is operated while a trunk key is depressed, the trunk key is only partially released and still maintains some of its contact springs in operated position. These springs are released subsequently when the receiver is replaced. In the circumstances just outlined, that is to say when a subscriber who has been speaking over a main exchange line wishes to refer to a subscriber accessible over the intercommunication system, the main exchange connection is held while this takes place and the speak- 492,837, and in Great Britain November 5, 1929.

ing circuit may then be transferred back to the main exchange line subsequently by the re-operation of the corresponding trunk key.

The invention will be better understood from the following description of one method of carrying it into effect which is given by way of example and should be taken in conjunction with the accompanying drawing.

In the system considered it is assumed that one or two particular stations are equipped for handling incoming main exchange calls by the provision of a bell permanently bridged across the trunk line in series with a condenser. The method of handling a call for a station not provided with such a bell would be that the station which replied to an incoming call on learning which party was required would signal that party over the intercommunication system and notify him that a call was awaiting him on the particular trunk line, whereupon he would press the corresponding trunk key and could then converse with the calling party as desired.

The station illustrated which is not equipped for the direct receipt of incoming main exchange calls comprises the usual transmitter T and receiver R which may be in the form of a handset and are electrically connected by means of the three-winding induction coil I arranged to give an anti-sidetone characteristic. The station is also provided with a dial having impulse springs IS and shunt springs SS for setting up main exchange connections while local connections are completed by means of the push button mechanism diagrammatically indicated at PB which may comprise a set of separate push-buttons or may be of the type in which a selecting knob is rotated to select the required station and then depressed. The signalling of the station is effected by means of a buzzer B operated by direct current. Trunk keys TKl and TK2 are also provided corresponding to two main exchange trunks and these have associated with them visual signals V1 and V2 for indicating the engaged condition of the trunks. Of the springs controlled by the trunk keys the three upper sets marked S are restored to normal. in case a push button is operated while the trunk key is depressed, while the lower set marked H still remain operated and are only restored when the receiver is replaced. For each trunk four leads are multiplied between the various instruments the leads S1 and S2 associated with the firsttrnnkbeing) for signallingpurposes while the leads T1 and T2 are the trunk conductors over which talk-- takes place. The intercommunication leads are multiplied throughout as usuallas are also the battery leads, (3+ and A+.

Study of the circuits will showthaitthe station can only be signalled while the switch hook springsSH are-in the norma-l position', a circuit being then completed over these springs and the individual"multiplelead"for the buzzer B.'- When the receiver is removed to' replyto'the call, the transmitter T re- 7 ceives current from the C battery over the by diallingin the usual manner.,.

Switch hook springs andnormal contacts of the trunk keys TKQ and TKl, the receiver circuit also including normal contacts of these keys. When the station. shown calls on the intercommunication system, the depression" of the appropriate button willi connect the common terminal with the corresponding individual stud and also with the com-- man ringingbar RB, thereby completing a 7 circuit from the A battery for the buzzer of.

the wanted party.

In case thesubscriber wishesto make amainexchange call, he will depress the trunk key, corresponding to a trunk which is not iniuse as indicated by the normal position.

\ of the associated visual? signal, whereupoir the intercommunication circuits w-illbe disconnected and he will'be connected through tola trunk-over which'hemay set-u ,hiscall f during. thecourse of either an incoming. or an out going main exchange callf he shouldlwishi'o consult alocal subscriber, he may press W the; corresponding push button whereupon the,

three upper sets of springs of the trunk. key

will bev released thus connectingup the intercommunication. speaking circuits. while the main exchange connection is held over:

thelower setof springs, the various visuall signals being also maintained operated When he: has concluded his local; c0nversa tion. and wishes to resumeconversati on with" the main exchange subscriber, he will. reoperate the trunk key thereby mechanically" releasing the push button and restoring the trunk circuits.

I According to the invention, therefore; a simple circuit-arrangementhas been designed whereby without undue complication local and main exchange service from the same instrument may readily be'providedin connection with an intercommunication system, and a, main automatic exchange.

What I claimas new and desire tosecureby, Letters Batent iisiz- 1 1, In combination with a telephone instrument of multi-station intercoimnunicating system normally connected for the extension of calls over such system, a manually operable element for selecting and signalling any other station of the system over a single wlre speaking-circuit, a two-wire trunk having a branch terminating in said telephone, and manually operable means for interrupting the normal connectionsto said telephone and, for. connecting the same to said trunk line.

2. In a telephone system, a telephone equipped-with a combined station selecting and signalling mechanism for use in establishingrlocal connections together; with other equipment including a switching device for connecting said telephone with a trunk line extending'therefrom to a distant exchange, means atsaidtelephonean'd at theother tel phones of such system 'for'indicating tl1'e busy-* condition'of'such trunk; and mea-ns enabling a subscriber toset up a local connection while; the trunk connection is held;

3. In a multi-station' intercommunicating system, subscribers instruments each' pro vided with a" combined" station selecting'and signalling mechanismior' use insetting up local connections, a pluralityof trunk'lines extending from an outside exchange andhav ing branches thereof terminating in the re spective instruments ofthe intercommunicat ingsyste'm, keys in said instruments individ ual to said trunksand 'operabletocomplete incoming" and outgoing connections thereover', andf'sign'als associated with saidinstru- Inents for'indicating' the busy or idle'condi tion of'the respective trunks.

4". In a multi-station intercommunicating. system, subscribers instruments each" pro vided'- with a combined station selecting "and signalling mechanism for use insettin 'up local connections, a plurality of trunk lines extending from an outside exchange and liav= mg, branches thereof terminating in the re-' spective instruments of' the intercommuni eating system, keys in said instrumentsindivid'uallto said trunks and operable to c0m'- pleteincoming and' outgoing. connections thereover,.andmeans enablinga subscriber to hold'a. trunkiwhile a local connection to any other station of said system is being setup.

5'.-1n a multi-station intercommunicating; system, subscribers instruments each provided with a combined'station selectingandi, signalling mechanism for use insettingup local connections, a plurality, oft'runk lines extendingfrom an outside exchange and.'having branches thereof'terminating in the respective instruments of the intercommunicating system, keysin said instruments individ ual'to said trunks andoperable to complete incoming, andoutgoing. connections thereover means enablinga subscriber to hold a trunkwhile alocal connection is beingset up, means. for. enabling. thev subscriber called to then connect his instrument with such trunk.

nal, and then connect a called station in talk- 6. In a telephone system wherein the telephones thereof are employed for both local and main exchange service; means manually rotated and then depressed to select, siging relation with a calling station; trunk lines having branches terminating in the respective telephones of said system, a switching mechanism at each station manually operated to disconnect its associated telephone from the local system and to connect it to one of said trunk lines, visual signals at all stations also operated consequent to the operation of the switching mechanism of any station, and means enabling the reconnection forthwith of the calling station with the local system while the trunk busy signal indications are maintained.

7 In an intercommunicating system in which a telephone instrument has a switch arm which is rotated manually, after the removal of the receiver from the switchhook at the calling station, to a position individual to another desired station of such system, is then manually depressed to operate the called station signal and upon release moves to an intermediate position to complete a talking circuit to the called line and wherein, when the receiver is replaced, the said arm again opens the previously established talking circuit; the provision of a trunk line terminating in such instrument provided with a manually operable switching device of the type which when operated, after the removal of the receiver at such station, remains in its operated position until restored to an intermediate position by a subsequent operation of the local switch arm and which fully restores from its fully operated or intermediate position consequent to the replacing of the receiver upon its switchhook.

8. In an intercommunicating system, a telephone instrument, connections extending from said instrument to all others of the system, trunk lines each having a branch terminating in said instrument, manually operable circuit controlling keys for said trunk lines and for completing connections between said telephone instrument and others of the system; contacts effective upon operation of one of said keys, following the removal of the receiver from its switchhook, to disconnect said instrument from its normally existing connection with the system as employed in intercommunicating service and to connect said instrument with one of said trunk lines; signals at the respective instruments of the system operable by other contacts of said key to indicate at all stations that the trunk has been taken for use; means controlled by a subsequent operation of another of said keys, prior to the restoration of the receiver, to partially restore the first operated key and to complete a connection to a local station while the specified trunk 

